During the coming year techniques for measuring cytotoxic activity of sera and lymphocytes against rheumatoid and nonrheumatoid synovial cells will be utilized to test for: (1) an antigen unique for RA cells or (2) an immune response of RA patients against normal synovial antigens. Work is being continued to establish cultures of separate cell lines from synovial tissue and synovial fluid specimens in order to test for latent viruses in several cell populations in addition to the previously tested synovial (mesothelial) cell.